A load binder is a device that is used to tighten a chain or cable to secure a load on a vehicle. A lever type load binder 11 is illustrated in FIG. 1. Movement of the lever 13 in the direction of the arrow shortens the distance between the two grab hooks 15 and 17. The lever 13 snaps over center at the end of its stroke and the chain tension holds the load binder closed. The grab hooks 15 and 17 are designed to grab chain links of a chain (not shown).
When load binders are tightened the degree of tension is in part determined by the distance between the links in the chain. Typical hooks used on load binders have a longitudinal slot through which one chain link passes with little clearance. Since adjacent chain links are at right angles, more or less, to each other, the next chain link cannot pass through the slot and the chain is held by the hook. The load binder may grasp the chain at any link and may be tightened. Typical chains are made of links that are all the same size, and so the tightness can be adjusted to the chain link that is closest to the tightest point the load binder can be tightened to. However, this may result in nearly a full chain link of looseness, if the binder cannot quite be tightened to the next link.
The inventor has proposed a solution to this problem in which the chain may be tightened in partial link increments instead of full link increments. The invention uses the principle that the length of the chain that is used up depends on the angle of the slot in the hook and interference between the chain and the body of the hook. The slot may be taken to lie in a plane. Over small angles, the closer a perpendicular to this plane is to being parallel to the direction of tightening, the less the amount of chain required to reach into the slot. Hence the invention provides a hook that is asymmetrical (the attachment end is offset from the hook end) so that when the chain enters the hook from one side it requires less length of chain than when it enters the other side. By appropriate choice of the amount of offset or asymmetry, the change in length required can be set to part of a chain link, preferably half a link.
While the invention has been described for use with a chain and load binder, it should be observed that the hook has utility to link anything that may be attached to the hook on one end with a chain on the other end.